Blue and Green or Blue and Yellow HYD fault light flashing on OVHD with no associated ECAM.
Cause: Associated engine oil pressure switch fault. That's right OIL pressure switch.
Airbag uses signal from engine oil px to tell other systems when the engine is running.... So perhaps, no signal from switch meant the ptu was armed, but not running since the edp was doing just fine... hence fault light but no action required?